NEW YORK (Dow Jones)–Ripples from the UBS AG (UBS) tax evasion case continue to reach other overseas banks, prompting them to put their houses in order – and even show uncooperative clients the door.

Copies of letters obtained by Dow Jones Newswires reveal several banks giving U.S. customers a deadline to provide tax details or see accounts closed. Some have simply told clients to take their assets elsewhere.

LGT Bank and Credit Suisse are among those threatening to oust some clients amid the uproar over UBS, which reached a settlement with U.S. tax authorities last month and agreed to turn over the identities behind 4,450 secret accounts.

A letter from Liechtenstein bank LGT Bank, for example, dated June 30, gave U.S. customers until this week to provide a completed Form W-9 and another form with U.S. tax details. LGT told recipients it would “terminate our business relationship with you in connection with the above-mentioned account” if the bank didn’t receive the information by Aug. 31.

The Department of Justice and Internal Revenue Service have consistently declined to say whether they are investigating specific banks beyond UBS. However, IRS officials said when they announced the settlement that the Swiss government has agreed to review and process additional requests for information from other banks on account holders “to the extent that such a request is based on a pattern of facts and circumstances equivalent to those of the UBS case.”

“I can assure you they are putting equal pressure on every offshore bank they can find,” says Black, whose firm, located in a hub of UBS activity, has created a special unit to deal with the large number of cases flooding in.

The LGT letter follows from the bank’s decision in early 2008 to scale down its business with U.S. clients, according to Christof Buri, a spokesman for the bank.

LGT told the U.S. Senate Permanent Subcommittee on Investigations in July 2008, during a hearing at which UBS also testified, that it had never actively pursued U.S. business. That business had always been of secondary importance to it in terms of volume and earnings, the bank said.

Unlike the LGT letter, which gives customers a chance to continue at the bank, a series of three letters from Credit Suisse Private Banking to U.S. clients simply instructs them that their accounts are being terminated. The letters are dated May 26, July 1 and July 14.

The July 14 letter says that if the recipient hasn’t provided information allowing Credit Suisse to transfer the assets to an account elsewhere by Aug. 14, the bank reserves the right to deposit the “relevant assets with the competent Swiss authority in accordance with applicable Swiss law or take other steps we deem appropriate to close the business relationship.”

Credit Suisse declined comment on the specific letters, but spokesman David Walker said in an email that in the normal course of business the company continues “to assess all client relationships.”

“We strongly believe we have the right compliance standards in place and adhere to all applicable laws,” Walker said in the email.

A letter from a third bank gives account holders until Sept. 30 to supply it with various tax-related documents, including a W-9 and a form declaring the offshore account to the IRS. The source who provided a redacted copy of the letter declined to identify the bank.

Asher Rubinstein, a partner at law firm Rubinstein & Rubinstein, LLP, says the push to get rid of U.S. clients or make sure their offshore accounts are tax compliant is hardly surprising, given the current move against tax havens by many governments. Foreign banks don’t want to be “the next UBS,” he says.

Now, he adds, banks are doing their own work to make sure accounts comply with tax rules, instead of taking clients’ word that they are filing all the right forms and paying their taxes.